阶梯溢流坝面坡度对一体化消能工水力特性的影响

为探求高水头、大单宽流量下坝面坡度对一体化消能工水力特性的影响,以阿海水电站为原型,采用三维k-ε双方程紊流模型,引入水气两相流VOF计算方法,利用几何重建格式来迭代生成自由水面,对1∶0.80、1∶0.75、1∶0.65三种阶梯面坡比进行数值模拟研究。结果表明:①最大负压值均位于首级阶梯立面凸角下1/4附近,并随坡度增加而增大。坡度为56.98°时,最大负压值为61.02 kPa,超过了6×9.81 kPa。②水流空化数在宽尾墩水舌出口位置出现最小值,空化数随坡度变陡而减小。坡度为56.98°时,空化数最小为0.358。坡度为51.34°时,空化数最大,为0.381。③随着阶梯溢流坝坝面坡度变缓,消力池最大临底流速增大。当坡度为51.34°时,消力池最大临底流速最大,达到26.84 m/s,超过了25 m/s,易发生冲磨破坏。当坡度为56.98°时,消力池最大临底流速最小,为24.00 m/s。消力池尾坎前最大临底流速随坡度增加而减小,坡度为56.98°时最小,为9.63 m/s;坡度为51.34°时,消力池尾坎前最大临底流速最大,为9.96 m/s。④坡度的变化对一体化消能工消能率的影响不大,坡度从51.34°增加到56.98°,消能率只提升0.15%。     

影响干式磁选机在石英除铁过程中的因素研究

本文通过对陕西某地石英矿进行干式磁选试验研究,介绍了给料速度、尾矿抛尾率、矿样含水率及含泥量等几个因素对干式磁选作用的影响,分析了干式磁选各因素在石英除铁过程中的规律,为后续工业应用提供一定的理论基础。     

不同镀层结构钢的耐盐雾腐蚀性能比较

通过盐雾试验模拟潮湿环境,对裸钢试片、电镀锌钢试片、化学镀镍-磷钢试片和化学镀镍-钴-磷钢试片进行了宏观形貌、微观形貌和腐蚀产物成分分析,比较了四个试片的耐盐雾腐蚀性能。结果表明:在盐雾环境中,四个试片均会发生电化学腐蚀,生成不同的腐蚀产物;在盐雾腐蚀周期内,裸钢试片的腐蚀速率最高,化学镀镍-磷钢试片和化学镀镍-钴-磷钢试片的腐蚀速率较低;四个试片在腐蚀过程中的阳极反应和阴极反应不同,腐蚀后的微观形貌存在明显差异。     

高固气比技术在2 500 t/d水泥熟料线的改造案例介绍*

采用高固气比悬浮预热分解技术对宝江2 500 t/d生产线烧成系统进行技改后,预热系统出口温度从351℃降低至279℃,粉尘浓度(标况下,以下同)从151.6 g/m3减少至43.9 g/m3,系统分离效率大幅提高;入窑生料分解率从90.5%提高至98%,生产线熟料烧成煤耗从119.4kg/t降低至100.80kg/t,熟料产量从2744t/d提高至3840t/d,各指标均属领先水平。     

Comparison study of thermochemical waste-heat recuperation by steam reforming of liquid biofuels

The concept of thermochemical exhaust heat recuperation by steam reforming of biofuels is considered. Thermochemical recuperation can be considered as an on-board hydrogen production technology. A schematic diagram of a fuel-consuming equipment with thermochemical heat recuperation is described. The thermodynamic analysis of the thermochemical recuperation systems was performed to determine the efficiency of using various fuels, in particular, methanol, ethanol, n-butanol, and glycerol. The thermodynamic analysis was performed by Gibbs free energy minimization method and implemented using the Aspen Hysys program. The thermodynamic analysis was performed for a wide temperature range from 400 to 900 K, for steam-to-fuel of 1, and pressures of 1 bar. The maximum fuel conversion reaches for the following temperatures: methanol - 600 K, ethanol - 730 K, n-butanol - 860 K, glycerol - 890 K. The dependence of the reforming enthalpy on temperature is determined. It was shown that the reaction enthalpy determines the heat transformation coefficient, which shows the ratio of the low heat value of synthetic fuel and the low heat value of the initial fuel. For all studied fuels, the maximum value of the transformation coefficient is observed for steam reforming of ethanol and the maximum heat transformation coefficient is 1.187. The temperature range is determined at which the maximum efficiency of the use of thermochemical recuperation occurs due to the reforming of biofuels. For methanol, the effective temperature is about 600 K, for ethanol is about 700 K, for n-butanol is 850 K, for glycerol is more than 900 K. The results obtained make it possible to efficiently select the type of fuel for thermochemical recuperation due to steam reforming.     

福建某低品位金矿新型浸金剂浸金试验

福建某斑岩型金矿品位低、规模大,金主要以自然金形式存在,可见金的粒度较粗,为高效利用该低品位金矿,开展新型浸金剂金蝉全泥浸出试验和柱浸试验,结果表明：全泥浸出在磨矿细度为-0.074 mm占80%、矿浆浓度25%、加石灰调pH 值11.0左右、初始金蝉浓度为500 mg/L和过程中控制金蝉浓度不小于300 mg/L条件下浸出20 h,金的浸出率为93.43%,金蝉耗量为1.02 kg/t；柱浸在矿石粒度为-30 mm条件下喷淋浸出23天,金累计浸出率和金蝉累计耗量分别为86.54%和1.22 kg/t。     

Predicting the damage development in epoxy resins using an anisotropic damage model

For fiber-reinforced plastics, the strain-rate dependent response is governed by the matrix behavior. In this work, the Goldberg model is considered for the epoxy matrix constitutive material model. Moreover, the strain-rate dependency is achieved by direct influence on the elastic modulus, the inelastic strain, and the material strain to failure. In addition, an anisotropic damage response is implemented and extended through a strain-rate dependent definition. Since the constitutive model relies on nonphysical parameters, a parameter study is further performed. Additional numerical investigations using a micro-mechanical model are performed. Tension and shear loading conditions are evaluated and the influence of different strain rates is explored. Furthermore, the implemented anisotropic damage model is compared and discussed against an isotropic damage model.     

地浸铀矿山浸出速度的影响因素

在地浸铀矿山生产过程中,铀的浸出速度是制约生产的重要参数,直接关系到矿山的服务年限。矿山生产采区往往存在严重的拖尾现象,为提高地浸铀矿山资源利用率,降低生产成本,研究了影响铀浸出速度的因素,提出了控制铀浸出速度的措施。     

55SiCr弹簧钢中的残留奥氏体与碳化物

通过扫描电镜(SEM)、电子背散射衍射(EBSD)、透射电镜(TEM)、X射线衍射仪(XRD)、热膨胀仪、洛氏硬度计等手段研究了弹簧钢55SiCr的组织和相变点以及残留奥氏体和碳化物在热处理过程中的组织演变。结果表明:55SiCr弹簧钢淬火后残留奥氏体以块状分布在基体上;随回火温度的升高,残留奥氏体减少并呈粒状和薄膜状分布;C在残留奥氏体中富集,使其稳定性增强;Si抑制了碳化物的析出,提高了残留奥氏体的稳定性。低温回火时,Si延缓了渗碳体析出;高温回火时,C原子扩散速率提高,促进渗碳体析出,引起体积的收缩。慢速加热回火时,C有足够的时间扩散,从而促进渗碳体的形成,使渗碳体的形成温度提前;快速加热回火时,C来不及扩散,抑制了渗碳体的析出。回火加热速率一样时,试验钢的硬度随回火温度的提高而下降。当回火温度为400 ℃时,硬度值最大为51 HRC;当回火温度为650 ℃时,硬度值最小为37 HRC。当加热速率为0.1 ℃/s时,硬度值最小为33 HRC;当加热速率为200 ℃/s时,硬度值最大为40 HRC。     

基于压力和流量守恒收敛准则的微织构端面机械密封数值计算

目前在研究微织构端面机械密封时,离散求解雷诺方程时采用的压力收敛准则,并不能完全保证得到准确的泄漏率。提出基于压力收敛和内外径流量守恒收敛双重收敛准则的微织构端面机械密封数值计算方法,针对圆柱形微孔端面机械密封,基于考虑JFO边界条件的二维雷诺方程,建立含一个计算域的数值计算模型,并采用不同的收敛准则对开启力和泄漏率进行数值计算。结果表明:仅使用压力收敛准则不能显式判断计算是否已经满足质量守恒,不能准确计算泄漏率;仅使用内外径流量守恒收敛准则可能出现迭代初始阶段就满足收敛条件,导致错误结果;使用压力收敛准则和内外径流量守恒收敛准则相结合的双重收敛准则,可保证泄漏率计算的正确性。